The effect of dietary protein and energy on feed intake and performance of laying hens.

Abstract:

This study was designed to devise a method by which the optimum combination of
dietary energy and protein could be found that maximises the margin over feeding cost in
an egg production enterprise. It was necessary to be able to predict feeding costs and
revenue associated with the use of a wide range of feeds varying in protein and energy.
To this end, two experiments were conducted using 256 Lohmann (128 White and 128
Brown) in the first, and 1296 Hy-line Brown laying birds in the second trial, that were 33
and 38 weeks old at the beginning of the two trials. Using the WinFeed 1.1 (1996) feed
formulation programme, four basal (corner) feeds were formulated in both experiments,
from which four protein and four energy contents (16 feeds) were produced in the first
experiment, and six protein and three energy contents ( 18 feeds) were used in the
second. Each feed was given to three replicates of 16 birds in the first trial, and to three
replicates of 24 birds in the second. The trials each lasted ten weeks, and the data
collected included food intake, change in body weight, egg weight and rate of laying.
Using the results from these two experiments and from previously published research, the
effects of dietary protein and energy on food intake were predicted independently, and
these predictions were then used to determine the cost of feeding. Similarly, egg weight
and rate of lay were predicted independently for changes in dietary protein and energy,
from which the revenue could be calculated over the range of energy and protein
contents. It is understood that a more integrated approach would be more accurate for this
purpose, but such an approach was beyond the scope of this investigation.
The use of contour plots based on regression analyses of the estimated income-minus-feeding
cost on changes in dietary protein and energy enabled evaluations to be made of
the effect on profitability of changes in egg price and maize price. And it was deduced
that under conditions in which the maize price is high, maximum profitability is achieved
with high energy and high protein content, irrespective of the price paid for eggs. When
the maize price is reduced, the combination of protein and energy that yields the highest
return over feed cost changes to low protein and low energy feeds. This change is
defensible on the grounds that the price of high-density feeds does not change as much as
that of low-density feeds when the maize price is lowered, whereas production, and hence
returns, remains the same, hence the low density feeds yield higher returns under such
circumstances.
The method applied in this study appears to be a useful tool for decision-making by egg
producers and nutritionists.